Slowing dow nAc motor in a fan

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Hi,

 

i have one of those classic white fans on stand for room. It has 3 speeds, but they are all waaaay to fast and now im thinking about how to reduce speed of the motor even further. In my theory, addind a capacitor in series should reduce actual voltage on the motor and slow it down?

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Last Edited: Wed. Jun 3, 2020 - 09:44 AM
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What type of motor is it ?

 

With many types of AC motor, the speed is set by the line frequency ...

 

Klemko wrote:
It has 3 speeds

So look at how they are achieved ...

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When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Well in most parts of the world the AC line voltage is about 220v, but here in the US it is 110v. 

If yours is 220, I would try using a 220/110 transformer and run it at half voltage and see if that will work for you. (Size the transformer for the load needed)

Other combinations are also possible and should be available for trial.

Jim

 

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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It has 3 speeds, but they are all waaaay to fast 

If you only want a wisp of air, why not rig up some PC or old laptop fans? 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Because for some stupid reason, the PCB part is glued into a case. Will pop it into my smd oven for a bit and hopefuly the case will open then.

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I had x 140mm on my desk, but my boss said that it looked too "janky"

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Ok, i managed to open it. Looks like the motor has multiple windings on the stator and so the 3 speed switch just changes which winding is energized. Soo i found the winding of the slowest speed and measured AC current to be 150mA.

 

So my logic is, if i add correct capacitor in series, the voltage on the fan stator winding will drop. 

According to math, the winding of the motor has around 1,5kOhm. So i could add capacitor, that equates to aroudn 500Ohms/50Hz in series. Which after math is 6,5uF/400V. And of course add a diode to protect aluminum capacitor in reverse halfwave.

 

Or stop being fancy and jsut plop in a 10W high voltage 470ohm resistor wink

Last Edited: Tue. Jun 2, 2020 - 12:06 PM
This reply has been marked as the solution. 
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You should be able to source a suitable motor start/run capacitor close to the required value. Don’t use an electrolytic.

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Klemko wrote:
Or stop being fancy and jsut plop in a 10W high voltage 470ohm resistor wink

But then he'll have to cool that with a fan. - I suppose the 140mm PC fan he already has will do the job.

 

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Which after math is 6,5uF/400V.

Try using one out of someone's air conditioner...you may have luck.  I've seen them in that range.

----

You could aim the fan in a different direction, so the wind would not be as tornadic, or whittle down the blades a bit  

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Klemko wrote:
I had x 140mm on my desk, but my boss said that it looked too "janky"

If this is a fan at your employer's office, I'm not sure whether you should touch it, In many companies I've come across if the Health & Safety Official discovered your mod, questions would be asked. The best outcome being the fan gets condemned.

 

Having said that however, my brother quietened his bedroom fan by using an old toroidal transformer from the junk box. We used only the split primary windings to halve the 230VAC, the secondary was left open-circuit.

 

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An autotransformer with variable tap would work nicely, too:

http://www.a1parts.ca/Variable_Transformers.htm

 

"Experience is what enables you to recognise a mistake the second time you make it."

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Last Edited: Tue. Jun 2, 2020 - 10:14 PM
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I found polymer capacitor for rigth values, ploped it in series with fan motor and now runs a bit slower and a lot quieter. 

Thanks for tip about proper capacitor type.

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Polymer capacitor? I'd expect a paper capacitor. I'd suggest you check the motor to see if it gets hotter. If it is an induction motor, they don't like running undervoltage and will get hot as a result.

 

something like this:

https://www.ebay.com.au/i/254453...

Last Edited: Wed. Jun 3, 2020 - 10:24 AM